Underrated Solution.

It's like that in all Python katas, Actual should equal Expected.

...'True should equal True' or 'true should equal true'

What? Then what's the error there?

Note that the difference between true and Trueis already in the description:

either "true"/"True" or "false"/"False" (check the sample tests about what capitalization to use in a given language).

For python this error message:
"When we pass in true, we want the string "true" as output: 'true' should equal 'True'"
could be a little more clear that the expected output is specifically with a capital T or F.

For esample instead of 'true should equal True', perhaps 'True should equal True' or 'true should equal true'

Same, instructions are not specifict as to what should be returned in JS